I horse traded into one of these field coil drivers when I met with another tube salvager like myself. At that point I knew nothing about what I had, other than obviously it was a field coil type. It looks outrageously beefy to me. The electro-magnet assembly is quite a bit larger than any of the console pull field coil drivers i have seen. The EIA code is 232 which makes it a Magnavox with a little searching I found out that it came from an organ or an organ tone cabinet. The field coil is 6000 ohms and schematics which I found show it in parallel with the power amp, not in series, like a choke. I decided that this speaker was interesting enough that I had better order another. I found one very affordably, and made it mine via the miracle that is online shopping...
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I had a case of 9v batteries in the shop, so I wired up a field supply by clipping a dozen of them in series, and connecting them to the field coil using jumpers. This allowed me to test the speaker to verify functionality, which I did, and it functions. Not likely to blow anything up with 9v batteries... The voice coil measured 6.3 ohms DC resistance so I felt safe treating it like any other 8 ohm coil. In free air it makes noise, which is better than the alternative. I decided, rather than building boxes for these to stuff them in my EV aristocrat cabinets just to get a sense of how they perform and weather or not I want to continue messing with them. I raided my parts stash and started on building a real power supply in my head. I started by finding some octal tube sockets which I can screw to the inside of my speaker cabinets, and use as connectors for not only the voice coil but for the field coils. I hoard organ parts so finding the pigtail took 30 seconds. I soldered in speaker wires to pins 1 and 5. I have not actually started to build a plug in the wall type power supply, but it should be fairly simple. The field coils want to see about 300 volts across them, Im pretty sure I have a rectifier tube and transformer which will do that... I have read just enough about field coils to be very curious. There are people claiming that they (field coil type drivers) are vastly superior to everything else, due to the (potential) increase in magnetic flux density in the coil gap. Others rave about "tripping over the thick sound". Needless to say I am rather intrigued. I do however want to maintain an open mind. I have less than $100 wrapped up in this project so I have essentially nothing to lose, everything to gain. I want to get a feel for these drivers and potentially build boxes for them at some point. Does anyone have any advice before I start? Am I wasting my time? Is the EV aristocrat corner horn a fair cabinet for this type of driver or should I try something else too?
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I had a case of 9v batteries in the shop, so I wired up a field supply by clipping a dozen of them in series, and connecting them to the field coil using jumpers. This allowed me to test the speaker to verify functionality, which I did, and it functions. Not likely to blow anything up with 9v batteries... The voice coil measured 6.3 ohms DC resistance so I felt safe treating it like any other 8 ohm coil. In free air it makes noise, which is better than the alternative. I decided, rather than building boxes for these to stuff them in my EV aristocrat cabinets just to get a sense of how they perform and weather or not I want to continue messing with them. I raided my parts stash and started on building a real power supply in my head. I started by finding some octal tube sockets which I can screw to the inside of my speaker cabinets, and use as connectors for not only the voice coil but for the field coils. I hoard organ parts so finding the pigtail took 30 seconds. I soldered in speaker wires to pins 1 and 5. I have not actually started to build a plug in the wall type power supply, but it should be fairly simple. The field coils want to see about 300 volts across them, Im pretty sure I have a rectifier tube and transformer which will do that... I have read just enough about field coils to be very curious. There are people claiming that they (field coil type drivers) are vastly superior to everything else, due to the (potential) increase in magnetic flux density in the coil gap. Others rave about "tripping over the thick sound". Needless to say I am rather intrigued. I do however want to maintain an open mind. I have less than $100 wrapped up in this project so I have essentially nothing to lose, everything to gain. I want to get a feel for these drivers and potentially build boxes for them at some point. Does anyone have any advice before I start? Am I wasting my time? Is the EV aristocrat corner horn a fair cabinet for this type of driver or should I try something else too?